Search results for "Vapor pressure"

Saturated vapour pressure of aroma compounds at various temperatures

2004

Abstract The aim of this study was to determine experimentally the vapour pressures of aroma compounds at various temperatures, especially at negative ones. The aroma compounds were: acetone, 2-butanone, 2-hexanone, 2-octanone, ethyl acetate, ethyl butanoate, ethyl hexanoate, n-hexanal, n-hexanol and γ-hexalactone. The technique used was a static device where vapour pressure was measured at equilibrium. The temperatures of analysis varied from −40 to 25 °C. Volatility of a pure compound depends on characteristics such as length of the aliphatic chain, the functional group and temperature. Among an homologous series, volatility increases when the aliphatic chain decreases and when temperatur…

Isobornyl Methacrylate as a Reactive Solvent of Polyethylene

2004

Solutions containing 15 wt, -% of a low-molar-mass polyethylene (PE) in isobornyl methacrylate (IBoMA), containing 0, 5 or 10 wt.-% of 1,4 butanediol dimethacrylate (BDDMA) as crosslinker, were polymerized using either benzoyl peroxide (BPO), at 80°C, or dicumyl peroxide (DCPO), with a thermal cycle attaining 150°C, as initiators. Phase separation of an amorphous PE-rich phase took place when carrying out the reaction at temperatures higher than the PE melting temperature. Partial crystallization of PE was observed when cooling to room temperature. Depending on the initial amount of BDDMA, the fraction of PE that was phase separated varied between 57 and 66% of the initial amount, with crys…

Sorption of n-hexane in amorphous polystyrene

2014

Sorption properties of pure n-hexane vapor in amorphous polystyrene (PS) were studied at 298 K by thermogravimetry under controlled vapor pressure. Two sorption-desorption cycles were performed by varying the relative pressure between 0 and 0.91. Mixing of PS with n-hexane resulted in a strong plasticization, which was evidenced by quite significant depression in the glass transition temperature of the polymer as shown by differential scanning calorimetry. Maximum quantity of n-hexane sorbed in the PS at 298 K and at a pressure close to saturation was about 12.4 wt %. The thermogravimetry yielded an isotherm with a strong hysteresis loop, explanation of which was hypothesized with the help …

Branched Versus Linear Polyisoprene: Flory-Huggins Interaction Parameters for their Solutions in Cyclohexane

2009

Flory-Huggins interaction parameters were determined as a function of composition for solutions of linear and of branched polyisoprene in cyclohexane (CH) at 25, 45, and 65 °C by means of vapor pressure measurements (moderate to concentrated solutions) and by vapor pressure osmometry (dilute solutions). The results demonstrate that CH is a considerably worse solvent for branched polyisoprene than for the linear analog at all temperatures and at all compositions. This observation corroborates the expectation based on a recent phenomenological approach, which accounts explicitly for the incapability of the segments of an individual polymer molecule to spread out over the entire volume of the …

PEO/CHCl3. Crystallinity of the Polymer and Vapor Pressure of the Solvent. Equilibrium and Nonequilibrium Phenomena

2003

Vapor pressures were measured for the system CHCl3/PEO 1000 (PEO stands for poly(ethylene oxide) and 1000 for Mw in kg/mol) at 25 °C as a function of the weight fraction w of the polymer by means of a combination of headspace sampling and gas chromatography. The establishment of thermodynamic equilibria was assisted by employing thin polymer films. The degrees of crystallinity α of the pure PEO and of the solid polymer contained in the mixtures were determined via DSC. An analogous degree of polymer insolubility β was calculated from the vapor pressures measured in this composition range. The experiments demonstrate that both quantities and their concentration dependence are markedly affect…

Experimental and estimated saturated vapour pressures of aroma compounds

1999

Abstract The saturated vapour pressure of d-linalool, 2-nonanone, d-limonene and isoamyl acetate were measured using a static method at different temperatures from 223 to 468 K. From the experimental values, Antoine's constants were determined to enable the calculations of the saturated vapour pressures at a given temperature. The saturated vapour pressure of the four aroma compounds at 298 K were respectively 27, 59, 200 and 733 Pa. These results were compared with those obtained using different estimation methods (Antoine–Grain, Watson, Lee–Kesler, Gomez–Thodos, Grain and Mackay). Gomez–Thodos' model was found to be the most accurate method for the estimation of the saturated vapour press…

Isobaric Vapor−Liquid Equilibrium for Ethanol + Water + Strontium Nitrate

1996

Isobaric vapor−liquid equilibrium for ethanol (1) + water (2) + potassium nitrate (3) at various concentrations of salt and with ethanol mole fractions from 0 to 0.642 has been measured at 100.0 kPa. The results were correlated by assuming that the salt was in ionic form and it was associated only with the water.

Isobaric vapor-liquid equilibria for binary systems composed of octane, decane, and dodecane at 20 kPa

1996

Vapor−liquid equilibria were measured for binary systems of octane + decane, decane + dodecane, and octane + dodecane at 20.00 kPa using a recirculating still. The results are thermodynamically consistent according to the point-to-point consistency test, and deviation from ideal behavior is small for all systems.

1984

By means of data from critical demixing and vapour pressure measurements and by inverse gas chromatography, including the results of published light scattering measurments, a consistent picture is obtained for the entire dependence of the Flory-Huggins parameter χ on the weight fraction w2 of the polymer and on the temperature T for the system tert-butyl acetate/polystyrene. Within the entire T-range (ca. 0°C – 140°C), χ increases stronger than exponentially with w2, the rise being the larger the larger χH (the enthalpy contribution to χ) becomes in the limit of infinite dilution. At sufficiently high temperatures (≳ 50°C), χH changes its sign from negative to positive as w2 is raised. This…